Inverter Generator Efficiency Calculator
What this calculator measures
Calculate electrical energy divided by fuel energy using matching fuel quantity and heating-value units. For example, use litres with kWh/litre or cubic metres with kWh/cubic metre. The energy-content default is illustrative.
Inputs and units
Use readings and ratings that describe the same equipment, operating interval, and measurement boundary. The sample entries are editable examples; they do not establish the specifications of your generator.
| Input | Example entry or choice |
|---|---|
| Average Power Output (W) | 2000 — enter a documented value |
| Runtime (hours) | 4 — enter a documented value |
| Fuel consumed (quantity in your chosen unit) | 2.5 — enter a documented value |
| Fuel energy content (kWh per matching fuel unit) | 8.9 — enter a documented value |
Calculation method
Efficiency % = electrical output kWh ÷ fuel input kWh × 100. Electrical output is average real watts multiplied by hours and divided by 1,000. Fuel energy is fuel quantity multiplied by energy content expressed per the same fuel unit.
For gas volumes, use the supplier’s reference conditions and corresponding calorific value. Identify whether the heating value is HHV or LHV; efficiency comparisons must use compatible conventions.
Worked example
2,000 W for four hours is 8 kWh. With 2.5 litres and an illustrative 8.9 kWh/litre heating value, fuel energy is 22.25 kWh and efficiency is 35.96%. For a gas quantity of 10 cubic metres, enter its kWh per cubic metre value, rather than treating the volume as litres.
Limitations and checks
This is a matched-interval energy ratio, not an efficiency curve inferred from generator size. Zero fuel input or readings implying efficiency above 100% are rejected; check units, interval boundaries, heating value, and measurements. Fuel-specific values vary, and an illustrative liquid-fuel default must not be reused unchanged for gas.
For a practical decision, keep the original readings, the generator model, the relevant manual or specification, and the assumptions alongside the result. A different load, site condition, rating basis, or unit convention can answer a different question even when the arithmetic is correct.
Sources and methodology
Publisher: CSP Digital Media Ltd. To report a formula, unit, or example error, contact us with the tool name, inputs, displayed result, and expected calculation.